To better understand the dynamic interaction between spatial structure, genetic architecture, and coevolution, we conducted a simulation study, exploring a range of situations plausible for the Taricha newt Thamnophis garter snake system.
To better understand the process of adaptive evolution across geographical space, this paper asks three main questions:
In particular, we compare different levels of mutational variance and polygenicity using individual-based simulations of continuous geographic space. The results complement field observations by describing situations that are consistent with empirical observations, and exploring other possible outcomes.
Experiment 1: varies both mutation rates and mutation effect sizes. Experiment 2: mutation rate was fixed for both species in each simulation, but allows the species to have different mutation effect sizes (and hence mutational variance). Experiment 3: mutational variance was the same for newts and snakes in each simulation, although polygenicity could be different (by varying mutation rate and mutation effect size).
Varies both mutation rates and mutation effect sizes. We ran the simulation normally, collecting data on how newt toxicity and snake resistance changed throughout the course of the simulation. We also ran the simulation without heritability and without the newt-snake interaction. All the following results are from a flat map.
What is the correlation between newt toxicity and snake resistance across geographical space within the simulation? Simulation varies both mutation rates and mutation effect sizes (Experiment 1). In these simulations there were different maps that created heterogeneous landscapes (cost gradient, interaction rate gradient).
What do local newt and snake phenotypes look like within the simulation? A few simulations from Experiment 1 (varies both mutation rates and mutation effect sizes) with a cost heterogeneous landscapes.
Does the speed of coevolution depends more on mutational variance than it does on polygenicity? Here we plot the Coevolution Speed (Phenotype Change/ Time), with results from experiment 2 and 3.
Experiment 2: mutation rate was fixed for both species in each simulation, but allows the species to have different mutation effect sizes (and hence mutational variance). Experiment 3: mutational variance was the same for newts and snakes in each simulation, although polygenicity could be different (by varying mutation rate and mutation effect size).
What is the relationship between population size and phenotype? This section examines results from experiment 1, 2, and 3 (from the early and late part of the simulation).
What is the relationship between phenotype/population size and GA? This section examines results from experiment 1, 2, and 3.